Field of the Invention
The invention relates to an image processing apparatus which collates a plurality of images, and a method which is used by the image processing apparatus.
Description of the Related Art
There is known a person retrieving technique of retrieving, out of image data photographed and captured by a plurality of cameras, when and by which camera a specific person was photographed. The person retrieving technique of that kind is usually applied to criminal investigation using mugshots, search for stray children using photographs of stray children's faces, and the like. In such fields to which the person retrieving technique is applied, since each camera has been installed at a different place, a photographing condition (including, e.g., a person's direction, an illumination condition, a lighting condition, and the like) for photographing a person is different for each camera. For this reason, a secure person retrieving technique in which an influence of the photographing condition of the kind is negligible is required.
In the person retrieving technique, the image data of each of registered persons and the image data of a person intended to be retrieved (i.e., a specific person) are collated (or compared) with each other, and the person of which a calculated degree of similarity in regard to the specific person is high is presented, thereby achieving the retrieval of the specific person. In the person retrieving technique like this, there has been provided a method which is secure about the photographing condition by adjusting such a collating process. Japanese Patent Application Laid-Open No. 2013-003751 discloses the method of reducing accuracy deterioration caused by the photographing condition, by using an image recognition technique of detecting the photographing condition from photographed and captured image data and adjusting a collation score based on the detected photographing condition. However, it is technically difficult to accurately detect the photographing condition such as the person's direction, the illumination condition, the lighting condition or the like, from the photographed image. For this reason, there is a case where the collation score is erroneously adjusted due to erroneous detection, so that the effect of reducing the accuracy deterioration is limited.
On the other hand, Japanese Patent Application Laid-Open No. 2009-163555 discloses the method of reducing accuracy deterioration caused by the photographing condition, by respectively adjusting a false acceptance rate (other-person acceptance rate) and a false rejection rate (person-in-question rejection rate) such that each of the relevant rates becomes a predetermined value, on the basis of the pairs of the image data of a person in question (a subject person) and the image data of other person (another person, a stranger or the like) collected for each camera. In the relevant method, the photographing condition is not detected, and instead the photographing conditions for the same camera are considered to be the same, so that it is possible to effectively adjust a collating process without erroneous detection.
However, in the related art, it is necessary to manually input correct answer information which indicates whether each of the pairs of the collected person image data indicates the person in question or the other person. Besides, when the collating process is adjusted based on a small amount of image data, the image data is adjusted unevenly or biasedly. Therefore, to prevent such inconvenience, a large amount of image data are necessary as learning data. For this reason, since it is necessary to manually input the correct answer information for the large amount of image data, it takes time and labor for the input, and the input itself is complicated. Thus, there is a problem that user-friendliness is low.
Consequently, the invention aims to reduce the work and trouble of the adjustment of the collating process.